fix: move --without-ncurses logic to scripts/checks.m4 per review

- Add TORRENT_WITHOUT_NCURSES macro in scripts/checks.m4
- Clear CURSES_LIBS/CFLAGS in the macro instead of if/else in configure.ac
- Restore simple LIBS/CFLAGS lines in configure.ac
- Add missing set_escdelay stub

src/display/curses_stub.h

@@ -99,6 +99,7 @@ inline int     init_pair(short, short, short) { return 0; }
 inline int     pair_content(short, short*, short*) { return 0; }
 inline int     resizeterm(int, int) { return 0; }
 inline int     getch() { return ERR; }
+inline int     set_escdelay(int) { return 0; }
 
 // getyx / getmaxyx are macros in real ncurses; stub them as no-ops
 #define getyx(w, y, x)     do { (y) = 0; (x) = 0; } while (0)